Route optiminzing in mobile ip providing location privacy

ABSTRACT

A routing method for routing data packets from a source terminal to a destination terminal via at least one communication network, said at least one communication network comprising at least one mobility agent entity for each of said terminals, the method comprising the steps of: establishing a route from the source via at least one first mobility agent, at least two consecutively arranged second mobility agents, to said destination, deciding that said route is to be optimized, rerouting said route from one of said at least one first mobility agents directly to one of the at least two consecutively arranged second mobility agents such that at least one intermediate mobility agent in said route is bypassed in the resulting rerouted route.

FIELD OF THE INVENTION

The present invention relates to a routing method and system for routingdata packets from a source terminal to a destination terminal via atleast one communication network.

BACKGROUND OF THE INVENTION

Recent developments in communication technology lead to communicationnetworks operating based on the Internet Protocol (IP). In connectionwith mobile communication, Mobile IP is thus becoming more and moreimportant. In communication networks, or network systems comprisingplural individual networks interconnected with each other, data areforwarded in units of so-called data packets from a source terminal to adestination terminal. A mobile source terminal is referred to as mobilenode MN, while a destination terminal (which may be a fixed or mobileterminal) is referred to as a correspondent node CN. Each of theinterconnected networks comprises at least one mobility agent entity foreach of said terminals. A mobility agent is any network entityimplementing functionalities supporting mobility of the terminal withinthe network/network system while assuring that communication remainspossible. For example, the expression “mobility agents” as used in thepresent text comprises

-   -   access routers (AR) enabling a terminal to access a respective        network,    -   home agents (HA) as a node of the home network that causes the        mobile node to be reachable at his home address even when the        mobile node is not attached to its home network (note that        non-home mobility agents take over the same tasks as home        agents, while non-home mobility agents are not located in the        node's home network, but rather in a visited network),    -   as well as edge routers (ER) (also known as gateways) providing        interconnection between different networks constituting a        network system.

As is generally known, Mobile IP includes a method of routing packetsthrough a Home Agent (HA) to provide mobility transparency to theCorrespondent Nodes (CN) and the Transport and Application layers in theMobile Node itself. Routing packets through the HA results in longroutes, especially when the MN is roaming in a networktopologically/geographically distant from the home network. This is alsoknown as the triangular routing problem.

Routing can be optimized through the usage of a dynamically assignedhome agent from the visited network, or using other locally assignedaddresses for communication with the Correspondent Nodes. This involvesletting the correspondent node CN know the binding between the HomeAddress and the Care_of_Address. Binding in this connection denotes atriplet of numbers that contains the mobile node's (MN) home address(permanent address, e.g. IP address), its temporary address, i.e. CoA,and the registration lifetime (i.e. how long the mobility agents may usethe binding).

GPRS networks as an example for mobile packet data networks managemobility in conjunction with the link layer connectivity in the cellularaccess network. The currently defined methods assign an address to theMN from the address pool of either the local GGSN or a GGSN in the homenetwork (GGSN=Gateway GPRS Support Node, GPRS=General Packet RadioService).

It is to be noted that GPRS represents an example of a network only towhich the present invention is applicable. The invention as subsequentlydescribed is, however, applicable to any routing of data packets from asource terminal to a destination terminal via at least one communicationnetwork, said at least one communication network comprising at least onemobility agent entity for each of said terminals. Also, the protocolused in such packet data networks is not limited to any specificprotocol type. For example, Mobile IP version 4 (IPv4) or version 6(IPv6), or GPRS specific protocols can be adopted.

An earlier patent application of Applicants which was filed in September2001 describes a method of managing a Mobile IP Binding Cache outside ofthe Correspondent Nodes in their access network routers.

Thus, the problem resides in providing an IP routing between a MobileNode MN and a Correspondent Node CN (often the correspondent node isitself a Mobile Node as well) where routing loops, or unnecessarily longroutes in general are avoided, and at the same time the location privacyof both communicating nodes is protected. Also, it is essential to thesystem responsiveness and scalability that no connection state as suchis required before the packets can be routed to the mobile node.Furthermore, signaling and other overhead over the air interface shouldbe avoided.

The key in location privacy is that the address(es) used in thecommunication with the correspondent node reveal no information aboutthe mobile's current location, or point of attachment in the packetnetwork topology. Such information is included and/or can be deducedfrom the Care Of Address, for example.

There are at least two ways to provide addressing meeting thiscriterion:

-   -   The address be statically assigned and never change. In this        way, no information about the current point of attachment is        revealed.    -   The address may be dynamically assigned, but from an address        pool that is not bound to any access network, or point of        attachment to the packet data network.

The second option above has the added benefit that the mobile's use ofthe network will be harder to profile over time, if different addressesare used at different times by the same mobile device.

When the address conveys no information about the current point ofattachment, the network must be able to map the address to an address inthe access network where the mobile node is actually attached. The pointin location privacy is that this mapping is hidden from thecorrespondent node.

Furthermore, to ensure the scalability of the network, the address usedin the communication must be routable—packets sent with the address mustreach a point in the network where the current location of the mobilenode is known, so that the packet may be further forwarded to the mobilenode in a timely fashion. The alternative, where a location look-up overthe network is required before the packet sent to the mobile can beforwarded at all has the problem that the packets need to be queued atthe origin access network while the location request is being served.This will cause initial delay, additional burstiness, and possiblepacket loss due to buffer overruns. Also, this will require locationlookup for every small session of communication, while it would havebeen more preferable to take a hit in the routing efficiency (if any)for the benefit of less location signaling and state maintenance. Such alook-up concept involving so-called location privacy agents is disclosedin Applicants former patent application filed with the US PTO under Ser.No. 09/986,602 on Nov. 9, 2001.

The above means that a rendezvous point like the Mobile IP Home Agent(HA) is essential to any connectionless packet network providingmobility with location privacy. But routing everything via the homeagent HA will cause unnecessary routing loops, especially when themobile node MN is roaming in networks topologically far away from thehome network, and is communicating with correspondent nodes outside ofthe home network. At an extreme this could for example mean to route thepackets from U.S. to Finland and then back from Finland to U.S., if themobile node's MN home agent HA is located in Finland, but the MN isroaming in the U.S. and communicating with an IP host in U.S.

Thus, from the foregoing it becomes clear that currently both GPRS andMobile IP solutions suffer from the lack of optimized mobility andlocation privacy at the same time. They can provide for either optimalrouting, or location privacy, but not both simultaneously.

SUMMARY OF THE INVENTION

Consequently, it is an object of the present invention to provide animproved routing method and system for routing data packets from asource terminal to a destination terminal via at least one communicationnetwork, which method is free from the above mentioned drawbacks.

According to the present invention, the above object is for exampleachieved by a routing method for routing data packets from a sourceterminal to a destination terminal via at least one communicationnetwork, said at least one communication network comprising at least onemobility agent entity for each of said terminals, the method comprisingthe steps of: establishing a route from the source via at least onefirst mobility agent associated to said source, at least twoconsecutively arranged second mobility agents associated to saiddestination, to said destination, deciding that said route is to beoptimized, and upon said decision, rerouting said route from one of saidat least one first mobility agents directly to one of the at least twoconsecutively arranged second mobility agents such that at least oneintermediate mobility agent in said route is bypassed in the resultingrerouted route.

In this connection, it is to be noted that rerouting can happen before asingle packet has been transmitted via the (initially) establishednon-optimized route. That is, the route may still be in the process ofbeing established or may have already been established. In each of thecases, an appropriate indication in a signaling such as resourcereservation signaling may trigger rerouting even before theestablishment of the (initial, non-optimized) route is actuallycompleted.

According to favorable further developments

-   -   said decision is taken at one of said at least two second        mobility agents associated to said destination,    -   said decision is based on an indication by the source or        destination to optimize the route or to request for a specific        quality of service for which route optimization is beneficial,    -   said decision is based on a service type of the traffic between        the source and the destination,    -   said decision to optimize the route is taken in case the service        type indicates a service imposing delay requirements,    -   said service type indicates real-time traffic,    -   said decision is based on an estimated benefit from route        optimization between said source and said terminal, and in case        said estimated benefit exceeds a predetermined threshold value,        it is decided to reroute said route,    -   said rerouting comprises the steps of informing one of said at        least one first mobility agents of a current care_of_address of        the destination,    -   said informing comprises the steps of sending a message from one        of said consecutively arranged second mobility agents to one of        said first mobility agents including the current care_of_address        of the destination,    -   said indication triggering the deciding for route optimization        is included in a resource reservation signaling.

Furthermore, according to the present invention the above object is forexample achieved by a routing system for routing data packets from asource terminal to a destination terminal via at least one communicationnetwork, said at least one communication network comprising at least onemobility agent entity for each of said terminals, the system comprising:route establishment means adapted for establishing a route from thesource via at least one first mobility agent associated to said source,at least two consecutively arranged second mobility agents associated tosaid destination, to said destination, decision means adapted fordeciding that said route is to be optimized, and, rerouting means,adapted to perform in response to said decision a rerouting of saidroute from one of said at least one first mobility agents directly toone of the at least two consecutively arranged second mobility agentssuch that at least one intermediate mobility agent in said route isbypassed in the resulting rerouted route.

According to favorable refinements of the present invention,

-   -   said decision means is located at one of said at least two        second mobility agents associated to said destination,    -   said decision is based on an indication by the source or        destination to optimize the route or to request for a specific        quality of service for which route optimization is beneficial,    -   said decision is based on a service type of the traffic between        the source and the destination,    -   said decision to optimize the route is taken in case the service        type indicates a service imposing delay requirements,    -   said service type indicates real-time traffic,    -   said decision is based on an estimated benefit from route        optimization between said source and said terminal, and in case        said estimated benefit exceeds a predetermined threshold value,        it is decided to reroute said route,    -   said rerouting means comprises informing means adapted for        informing one of said at least one first mobility agents of a        current care_of_address of the destination,    -   said informing means comprises sending means adapted to send a        message from one of said consecutively arranged second mobility        agents to one of said first mobility agents including the        current care_of_address of the destination,    -   said indication triggering the decision means for deciding for        route optimization is included in a resource reservation        signaling.

By virtue of the present invention an advantageous routing method whichsimultaneously provides for optimal routing and for location privacy isrealized, i.e. the location information of the destination is not leakedto the source or other non-trusted entities in the network

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, the present invention will be described in greaterdetail with reference to the accompanying drawings, in which

FIG. 1 shows a routing scenario in a packet network where the accessrouter AR is a mobility agent, but where route optimization is notperformed;

FIG. 2 shows a routing scenario in a packet data network according tothe present invention;

FIG. 3 shows a routing scenario in a packet network system comprisingtwo individual networks where the access router AR is a mobility agent,but where route optimization is not performed; and

FIG. 4 shows a routing scenario in a packet data network systemaccording to the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The present invention will now be described in detail with reference tothe drawings.

FIG. 1 shows a routing scenario in a packet network in order to enhanceunderstanding of the invention as illustrated in FIG. 2 showing arouting scenario in a packet data network according to the presentinvention. Note that the same notation and reference signs are usedthroughout the Figures.

FIG. 1 illustrates an example in which only one single network, aso-called mobile network NW1 is present. This could be the case for awhole global network such as the Internet. The notation of the arrowsexemplifies that a packet of the indicated number is transmitted, thenumber being also representative of a sequence of the transmission stepswhen routing a packet to be sent from a source to a destination.Following the number, the source of the packet is indicated, and “>”indicates that the packet is to be delivered/routed to the subsequentlyindicated destination. The expression in brackets following thedestination represents an encapsulated addressing scheme (binding) whichindicates the inner source and inner destination to which the respectivepacket is to be routed. This will become more apparent when referring tothe following explanations.

Furthermore, MN1, MN2 denote mobile nodes acting as a source as well asa destination, respectively. The mobile nodes are identified andaddressable by their home addresses H1, H2, respectively. Each of themobile nodes access the network NW1 via an access router AR1, AR2,respectively, as a mobility agent for a respective one of saidterminals. In addition, the network is provided with a respective Homeagent HA1, HA2, respectively, for said mobile node MN1 and/or MN2. Eventhough it may not be excluded that HA1 and HA2 are locally close to eachother or located at the same site, for the further explanations it isassumed that they are physically different entities. The same applies tothe access routers as it is assumed that the source and destinationterminals are geographically distant from each other so that they haveto rely on the use of different access routers for accessing thenetwork.

Now, a routing is described as illustrated in FIG. 1. Initially, mobilenode MN1 with address H1 as the source addresses a packet in a firststep 1 to the destination, i.e. mobile node MN2 with address H2, asdenoted by 1:H1>H2. This reaches the access router AR1 responsible toprovide network access to the mobile node MN1. The access router AR1, ina second step 2, forwards the received packet to the home agent HA2 incharge of supporting mobility for the destination mobile node MN2. Theaccess router knows which home agent is in charge on the basis of theaddress H2 of the destination MN2; the packet is encapsulated and sentto the home agent HA2, as denoted by 2:AR1>HA2(H1>H2). Subsequently,step/packet 3, the home agent HA2 knows that for the addressed mobilenode MN2 (address H2), access router AR2 is in charge and routes thepacket to this access router, as denoted by 3:HA2>AR2(H1>H2). Finally,access router AR2 delivers the packet to the addressed destination MN2with address H2. Note that dependent on the location of MN2 in thenetwork, another access router, e.g. AR3 (not shown) could be contactedby the HA2. Thus, the access routers' addresses represent acare_of_address of the respective terminal associated thereto. Note thatin steps 1 to 4 the same packet contents is forwarded/routed from MN1 toMN2 and only the packet header changes during routing due to theencapsulation.

Thus, after step 4, the initial packet to be routed from the source tothe destination has been delivered from MN1 to MN2. Assuming that MN2answers the message received from MN1, the packet flow is as denoted inFIG. 1, i.e. from MN2 to AR2 as denoted by 5:H2>H1, then from AR2 to HA1as denoted by 6:AR2>H1(H2>H1), then from HA1 to AR1 as denoted by7:HA1>AR1(H2>H1), and then from AR1 to MN1 as denoted by 8:H2>H1.

Apparently, there is established a route 1, 2, 3, 4 (from MN1 to MN2)and/or 5, 6, 7, 8 (from MN2 to MN1) from the respective source MN1/MN2via a first mobility agent AR1/AR2 associated to said source, at leasttwo consecutively arranged second mobility agents HA2, AR2/HA1, AR1associated to said destination, to said destination MN2/MN1.

Every subsequent packet from MN1 to MN2 and vice versa will take thesame routing through the network and will involve such a triangularrouting of e.g. AR1->HA2->AR2. This may represent a rather long distancecausing undesirable delays.

The present invention, when adhering to the example of FIG. 1 proposes asolution as illustrated in FIG. 2. Namely, once it is decided that saidestablished route is to be optimized, and upon said decision, rerouting5, 7 of said established route is performed from said first mobilityagent AR1 directly to the last one AR2 of said consecutively arrangedsecond mobility agents HA2, AR2 such that one or more HA2 intermediatesecond mobility agents in said established route are bypassed in theresulting rerouted route 6, 7, 4.

In this connection, it has to be noted again that for explanatorypurposes the drawings are simplified. Thus, it should be kept in mindthat basically it is not required for the invention that the *first* onedoes the rerouting to the *last* one. The only condition is be that thepath is significantly shortened by the route optimization. For example,it may be that a 2^(nd) mobility agent reroutes the packets to a 5^(th)one, thus by-passing 3^(rd) and 4^(th) ones. More generally, there isestablished a route from the source via at least one first mobilityagent associated to said source, at least two consecutively arrangedsecond mobility agents associated to said destination, to saiddestination, decided that said route is to be optimized, and upon saiddecision, a rerouting of said route from one of said at least one firstmobility agents directly to one of the at least two consecutivelyarranged second mobility agents is performed such that at least oneintermediate mobility agent in said route is bypassed in the resultingrerouted route. Simultaneously, this is done so that the locationinformation of the destination is not leaked to the source or othernon-trusted entities in the network. This will be explained in moredetail in the following. A comparison of the packet flow between FIGS. 1and 2 reveals that steps 1 to 4 are identical. Hence a repeateddescription thereof is omitted. As an option, once a packet has reachedMN2, a trigger input can be given from MN2 via AR2 to HA2, which triggerinitiates rerouting the established route to a rerouted one. The homeagent HA2 knows that packets to MN2 (address H2) have to be routed viaAR2 to MN2. Thus, either upon receipt of the packet in step 2 oroptionally upon receipt of the trigger, HA2 informs the access routerAR1 in step 5 that packets with destination MN2 (address H2) are to berouted to AR2, as denoted by 5: HA2>AR1[H2=>AR2]. The expression in “[]” denotes the binding in payload.

Upon such rerouting a subsequent packet from MN1 at step 6 to AR1, AR1will route the packet in step 7 directly to AR2, as denoted by7:AR1>AR2(H1>H2), thereby bypassing HA2 for this and the subsequentpackets. Stated in other words, the rerouting comprises the step “5” ofinforming said first mobility agent AR1 of a current care_of_address AR2of the destination, wherein said informing comprises the steps ofsending (5) a message from the first one HA2 of said consecutivelyarranged second mobility agents to said first, AR1, mobility agentincluding the current care_of_address of the destination.

Thus, routing distance is shortened, delivery of packets becomes fasterand delay sensitive applications may benefit from such a routing.Simultaneously, the CoA of MN2, is not revealed to the source MN1.Rather, the CoA of MN2 is only informed to AR1 and kept within thenetwork. Hence, location privacy of MN2 is maintained while routing isoptimized. Of course, in case MN2 moves so that another AR becomes“responsible”, the binding will be updated.

As regards the decision for initiating route optimization, said decisionis taken at one of said at least two second mobility agents associatedto said destination, i.e. at HA2 or AR2. Since HA2 is the first of themobility agents associated to MN2, it could be preferred to let HA2decide on whether to perform route optimization or not.

The decision is for example based on an indication by the source tooptimize the route. In this case, a packet sent from MN1 to MN2includes, e.g. in its header, a corresponding indication such as aspecific bit set to a predetermined value indicating that the routing isto be optimized.

Also, said decision can be based on a service type of the trafficbetween the source and the destination. In such a case, the service type(of the application to which the packet belongs) is indicated in thedata packet or a signaling message. The mobility agent checks whetherthe service type of the packet matches a predetermined service type forwhich route optimization is to be performed, and if so, performsoptimization as described above. Examples for such a service type may bea service type indicating a service imposing delay requirements, such asindicating real-time traffic.

Additionally or alternatively to the above, said decision can be basedon an estimated distance between said source and said terminal, and incase said estimated distance exceeds a predetermined threshold distancevalue, it is decided by said mobility agent to reroute said establishedroute, as described above. Stated in other words, the mobility agent(e.g. HA2 in the above example) evaluates/estimates the length of thepacket route and dependent on the estimation decides to reroute packets.Thus, any packet may be rerouted dependent on the route length or onlypackets of a specific service type are rerouted dependent on the routelength estimation.

Note that although FIG. 2 shows the route optimization for one directiononly (MN1->MN2), the same principles apply for the other direction, i.e.MN2->MN1. However, this is not shown in FIG. 2 in order to keep thedrawing simple. In such a case, HA1 would inform AR2 that AR2 has toroute packets intended for MN1 from AR2 to AR1, bypassing HA1.

FIG. 3 shows a further routing scenario, but now in a packet networksystem comprising two individual networks NW1 and NW2, and FIG. 4 showsa routing scenario in such a packet data network system according to thepresent invention.

In FIG. 3 it is assumed that MN1 (address H1) as a source attached tonetwork NW1 communicates with an external correspondent node EN_(x)(address E_(x)) attached to another network NW2. The structure ofnetwork NW2 is transparent for the question of routing in connectionwith the present invention, as only the routing in network NW1 isfocused here. Nevertheless, in network NW2 similar procedures can beestablished, however, these are omitted here from the description andillustration. As in FIGS. 1 and 2, associated to MN1 are an accessrouter AR1 and a home agent HA1, both located in network NW1. Thenetworks NW1 and NW2 are interconnected by means of so-called edgerouters or gateways ER_(n) and ER_(m). The edge routers ER can beidentical, but can be topologically separated from each other. Here, thesecond case is assumed. Thus, agent ERm is fixedly assigned for routingtraffic from NW1 to NW2, while ERn is assigned for the reverse trafficdirection, i.e. NW2 to NW1.

The same notation regarding the signals/steps as in FIGS. 1 and 2explained above also applies to FIGS. 3 and 4.

As shown in FIG. 3, MN1 sends a packet to ENx, as denoted by 1:H1>Ex,which initially reaches AR1. AR1 knows, e.g. based on the address Ex ofENx that edge router ERm is to be used for routing this packet, androutes the packet to ERm, as denoted by 2:AR1>ERm(H1>Ex). Then,transparent for the routing in NW1 the edge router ERm forward thepacket to ENx, as denoted by 3:H1>Ex. When responding to the receivedpacket, ENx forwards a packet to and/or via ERn as it knows that H1 inNW1 can be reached but via ERn, as denoted by 4:Ex>H1. ERn in turn,based on the address H1 of MN1 contacts the associated home agent HA1 inNW1 and forwards the packet to HA1, as denoted by 5:ERn>HA1(Ex>H1). Thehome agent knows that MN1 can be reached by its CoA, and forwards thepacket accordingly, as denoted by 6:HA1>AR1. The access router AR1 inturn forwards the packet to the mobile node MN1, as denoted by 7:Ex>H1.It is to be noted here that from step 4 onwards the external node ENxacts a source and the mobile node MN1 acts as a destination. Thusrouting from MN1 to ENx follows the route MN1->AR1->ERm->ENx, while inreverse direction it follows the route Enx->ERn->HA1->AR1->MN1.

Thus, within network NW1, packets routed to the mobile node MN1 (fromthe source in the external network NW2) are passing via the rather longroute from ERn to HA1 to AR1 and then to MN1.

According to the present invention, when applied to this scenario, suchdrawback is prevented, as will become apparent from FIG. 4.

The present invention, when adhering to the example of FIG. 3, proposesa solution as illustrated in FIG. 4. Namely, once it is decided thatsaid established route (to recapitulate: established route isrepresented by 4, 5, 6, 7) is to be optimized, and upon said decision,rerouting 8, 10 of said established route is performed from said firstmobility agent ERn directly to the last one AR1 of said consecutivelyarranged second mobility agents HA1, AR1 such that one or more, HA1,intermediate second mobility agents in said established route arebypassed in the resulting rerouted route 9, 10, 7.

This will be explained in more detail in the following. A comparison ofthe packet flow between FIGS. 3 and 4 reveals that steps 1 to 7 areidentical. Hence a repeated description thereof is omitted. As anoption, once a packet has reached AR1, a trigger input can be given fromAR1 to HA1, which trigger initiates rerouting the established route to arerouted one. The home agent HA1 knows that packets to MN1 (address H1)have to be routed via AR1 to MN1. Thus, either upon receipt of thepacket in step 5 or optionally upon receipt of the trigger, HA1 informsthe edge router ERn in step 8 that packets with destination MN1 (addressH1) are to be routed to AR1, as denoted by 8: HA1>ERn[H1=>AR1]. Theexpression in “[ ]” denotes the binding in payload.

Upon such rerouting a subsequent packet from ENx at step 9 to MN1, ERnwill route the packet in step 10 directly to AR1, as denoted by10:ERn>AR1(Ex>H1), thereby bypassing HA1 for this and the subsequentpackets. Stated in other words, the rerouting comprises the step “8” ofinforming said first mobility agent ERn of a current care_of_address AR1of the destination, wherein said informing comprises the steps ofsending, 8, a message from the first one HA1 of said consecutivelyarranged second mobility agents to said first, ERn, mobility agentincluding the current care_of_address of the destination.

Thus, routing distance is shortened, delivery of packets becomes fasterand delay sensitive applications may benefit from such a routing.Simultaneously, the CoA of MN1, i.e. AR1 is not revealed to the sourceENx. Rather, the CoA of MN1 is only informed to ERn and kept within thenetwork NW1. Hence, location privacy of MN1 is maintained while routingis optimized. Of course, in case MN1 moves so that another AR becomes“responsible”, the binding will be updated.

It is to be noted that the present invention can be implemented atnearly any time by taking the decision to reroute the established route.Therefore, the explanation referring to an initial “first” packet andsubsequent “second” packet has been chosen as a mere example forenhancing understanding of the invention. As regards the decision to betaken, e.g. by HA1 in the case of FIG. 4, the same principles asexplained before in connection with FIG. 2 apply.

Stated in other words, as mentioned above, it is very likely that mostof the time routing via the HA will not cause any significant routinginefficiency, for example, when the subscriber is located close to hishome, and the Home Agent situated topologically “close by” is used, nosignificant saving can be attained by route optimization. In general, itshould therefore be decided on a case-by-case basis, whether routeoptimization will result in saving of delay, or network resourcesoffsetting the cost of the route optimization related signaling andstate maintenance. Taking such a decision can be based on criteria asexplained above, while of course additional criteria may also beapplied.

Taking the above into consideration it is the Home Agent itself, who hasall the information needed to make the decision for the routeoptimization. Home Agent sees the address of the correspondent node CN,as well as the current care-of address CoA of the mobile node. The homeagent can also profile and/or monitor the traffic between the two anddecide if and when to initiate route optimization. Optionally, the AR oreven the MN itself could be utilized in triggering the routeoptimization and thus reducing the burden on the Home Agent related tofollowing the traffic patterns being forwarded. An example of this couldbe some resource reservation signal originating from the MN forrequesting certain Quality of Service for a forthcoming traffic stream(e.g. real.time traffic). If low delay is requested, the related HomeAgents could be asked to proactively arrange route optimization todecrease the end-to-end transmission delay.

Route optimization itself cannot be performed by the Mobile Node, or theCorrespondent Node, since doing that would reveal the care_of_address ofthe other party to the other, and thus having no location privacy. Dueto this the care-of addresses of the communicating entities need to bekept inside the network (Mobile Network). Mobility Agents at the edgesof the network will take care of the route optimization, as signaled bythe home agents.

The Access Routers providing network access for the Mobile Nodes willtake care of the route optimization and are trusted not to reveal thecare-of address of the correspondent node to the mobile node they areserving. Edge routers interfacing the other networks will terminate allmobility and route optimization related signaling to guard the locationrevealing information from leaking to non-trusted networks/entities.

In an ideal case, the whole global network (e.g. the Internet) would bemobile (the Mobile Internet) and utilizing this invention (FIG. 2). Butin the meanwhile it is likely that mobility will emerge in individualnetworks, or coalition of networks with interest in mobility andprotecting their customer's location privacy while providing bestpossible network service. An example of this situation with the presentinvention implemented is given in FIG. 4. The key to note here is thatthe Mobile Network is multi-homed, and has several edge routersinterfacing to other networks. The same home addresses will be reachablethrough any of the edge routers. Note that the internal path length inthe Mobile Network is not made visible to the external networks. Therouting metrics will cause the shortest external path to be selected, sothat an edge router closest to the correspondent node will be used tocommunicate with the mobile node. This is essential to the routeoptimization, since the edge router will in general remain in the pathirrespective of the mobility optimizations done inside the mobilenetwork.

The edge router will then tunnel the packet sent to the mobile node'shome address to the MN's Home Agent. The tunneling method used isimmaterial, but it is essential that the edge router's address will becarried or otherwise made known to the Home Agent. The Home Agent willfurther forward the packet to the access router serving the Mobile Node.

Various optimization schemes may be utilized to reduce the tunnelingoverhead within the network itself. It should be noted that thisinvention does not call for tunneling over the air interface (theinterface between the MN and an Access Router).

In the reverse direction, the MN will send it's packets with it's HomeAddress as the source address. The AR will authorize the MN's use of thespecific Home Address by communicating with the Home Agent eitherdirectly or via other mechanisms, such as AAA (e.g. via the Diameterprotocol). The rest of the Mobile Network will trust on the accessrouters to block any unauthorized source addresses. The edge routerswill enforce this by not forwarding packets out of the Mobile Networkwith source addresses out of the pool of Home Addresses valid in theMobile Network.

The destination address used in the packets sent by an MN in the MobileNetwork is the address of the correspondent node known to the MN. It canbe a home address of another Mobile Node either in the same or differentnetwork, or a normal IP address of a fixed node in either the MobileNetwork itself or an external network. Normal IP routing will cause anoptimal (shortest) path to be taken to the destination address. If thedestination address is a home address, it will reach the Home Agent ofthe destination, from where it is forwarded to the access router of thedestination. If the destination's Home Agent will want to utilize routeoptimization, the HA will send a Binding Update towards the AccessRouter or an Edge Router who sent the packets to the HA. (this willinitiate rerouting, as explained herein before.)

The initial network access registration is required to convey the MN'sHome Address from the Home Network to the Access Router (AR). After thisthe AR will allow the MN to send packets with the Home Address as thesource address in the IP packets. The AR's address can be used as theCare-of Address (CoA) for the MN, if IP-in-IP tunneling (or equivalent,such as GRE or GTP) is used for the transport of user's packets in theMobile Network. Alternatively, the AR may allocate an unique CoA for theMN, allowing the AR to provide a one-to-one mapping between the CoA andthe Home Address, enabling optimized encapsulation in most cases.

FIGS. 3 and 4 show a MN of the Mobile Network communicating with anexternal node ENx in another network. The likely possibility ofasymmetric paths (different Edge Routers for the two directions) is alsoillustrated and explained before. Binding Update with the externalnetwork is shown below in FIG. 4. Essentially the Edge Routers maintainBinding Caches for the correspondent nodes in the other networks. Noinformation about the MN's current location is sent to the othernetworks.

The address ownership management will be made easier by the fact that itis the HA owning the address that will be involved in the binding updateprocess. Access and Edge Routers can be configured to accept bindingupdates from known Home Agents of the Mobile Network only. After theBinding exists the tunnel endpoints are responsible of refreshing thebinding. The refreshing need not necessarily happen via the Home Agent.

Optionally, the access routers could initiate the binding updateswithout involving the home agents directly, but that requires the HomeAgent to use the sending AR's address as the tunnel source address whenforwarding the packet to the destination AR. This way the destination ARknows of the source AR, and will be able to decide whether to do anbinding update or not.

Different versions of the Internet Protocol (IP) can be used for theservice to the MNs and the transport inside the Mobile Network. Forexample, MN's could be provided with IPv6 service, even when theinternal transport in the Mobile Network is utilizing IPv4.

The invention is applicable to the GPRS networks. Here the GGSNs are theAccess Routers. Home Address of the MN could be fetched from theHLR/HSS. Subscriber's home operator would maintain Home Agents, wherethe current GGSN under which the Mobile is located is known. Edgerouters would be managing Binding Caches for the mobiles of the GPRSnetwork, enabling optimal routing. The tunneling method utilized couldbe the GPRS Tunneling Protocol (GTP).

Optimally, the GPRS network has Edge Routers situated on all the majorgeographical locations. This makes the mobile network span widestpossible area, enabling route optimization. Packets from externalnetworks would be routed to the GPRS network through the Edge Routerclosest to the traffic source, allowing the GPRS network to provideoptimal routing without revealing any location information to theexternal network entities.

The established roaming agreements should be utilized to allow differentGPRS networks to be combined into a federated network, inside of whichthe location information (current point of attachment) could be utilizedto provide the best routes.

The present invention as outlined above proposes that resourcereservation signaling should indicate that routing optimization shouldbe performed. Also, for example, the Edge Routers maintain BindingCaches for the correspondent nodes in the other networks. No informationabout the MN's current location is sent to the other networks. The wholedefinition of the “Mobile Network” involves trust between the elementsin the Mobile Network. For example, if an external node would try to useEdge Router's or Access Router's address as the source address, thatwould be spotted on one of the routers on the edge of the Mobile Network(ingress filtering). In addition, it is not unfeasible to have internalkeying infrastructure covering the network elements of the mobilenetwork. So the tunneling between ARs/ERs and the HAs would need to becovered by (possibly transitive) trust relationships between them. Theinvention proposes the HA to terminate the tunnel the ER (or AR) sendsto it. The tunneling from the HA to the target MN would happen normally,assuming that the “AR” is provided to the HA as the care-of address.

Accordingly, as has been described herein above, the present inventionconcerns a routing method for routing data packets from a sourceterminal MN1, H1; Enx, Ex to a destination terminal MN2, H2; MN1, H1 viaat least one communication network NW1; NW1, NW2, said at least onecommunication network comprising at least one mobility agent entity HA1,HA2, AR1, AR2, ERn, ERm for each of said terminals, the methodcomprising the steps of: establishing a route 1, 2, 3, 4; 4, 5, 6, 7from the source MN1, H1; Ex, ENx via at least one first mobility agentAR1; ERn associated to said source, at least two consecutively arrangedsecond mobility agents HA2, AR2; HA1, AR1 associated to saiddestination, to said destination MN2, H2; MN1, H1, deciding that saidroute is to be optimized, and upon said decision, rerouting said routefrom one of said at least one first mobility agents AR1; ERn directly toone of the at least two consecutively arranged second mobility agentsAR2; AR1 such that at least one intermediate mobility agent HA2; HA1 insaid route is bypassed in the resulting rerouted route. The presentinvention also concerns a corresponding system.

In detail, even though not expressly depicted in the drawings, theforegoing description of the present invention apparently also disclosesa routing system for routing data packets from a source terminal (MN1,H1; Enx, Ex) to a destination terminal (MN2, H2; MN1, H1) via at leastone communication network (NW1; NW1, NW2), said at least onecommunication network comprising at least one mobility agent entity(HA1, HA2, AR1, AR2, ERn, ERm)) for each of said terminals, the systemcomprising: route establishment means adapted for establishing a route(1, 2, 3, 4; 4, 5, 6, 7) from the source (MN1, H1; Ex, ENx) via at leastone first mobility agent (AR1; ERn) associated to said source, at leasttwo consecutively arranged second mobility agents (HA2, AR2; HA1, AR1)associated to said destination, to said destination (MN2, H2; MN1, H1),decision means adapted for deciding that said route is to be optimized,and, rerouting means, adapted to perform in response to said decision arerouting of said route from one of said at least one first mobilityagents (AR1; ERn) directly to one of the at least two consecutivelyarranged second mobility agents (AR2; AR1) such that at least oneintermediate mobility agent (HA2; HA1) in said route is bypassed in theresulting rerouted route.

The decision means is located at one of said at least two secondmobility agents (HA2, HA1) associated to said destination.

Said decision is based on an indication by the source or destination tooptimize the route or to request for a specific quality of service forwhich route optimization is beneficial. Alternatively and/oradditionally, said decision is based on a service type of the trafficbetween the source and the destination. For example, said decision tooptimize the route is taken in case the service type indicates a serviceimposing delay requirements, e.g. said service type indicates real-timetraffic.

Said decision is based on an estimated benefit from route optimizationbetween said source and said terminal, and in case said estimatedbenefit exceeds a predetermined threshold value, it is decided toreroute said route. The benefit can be measured/expressed in a delayreduction (as compared to non-optimized routing, which in turn maycorrespond to a (shortened) distance between source and destination).

Said rerouting means comprises informing means adapted for informing oneof said at least one first mobility agents of a current care_of_addressof the destination, wherein said informing means comprises sending meansadapted to send a message from one of said consecutively arranged secondmobility agents to one of said first mobility agents including thecurrent care_of_address of the destination.

Said indication triggering the decision means for deciding for routeoptimization is included in a resource reservation signaling.

While the invention has been described with reference to a preferredembodiment, the description is illustrative of the invention and is notto be construed as limiting the invention. Various modifications andapplications may occur to those skilled in the art without departingfrom the true spirit and scope of the invention as defined by theappended claims.

1. A routing method for routing data packets from a source terminal(MN1, H1; Enx, Ex) to a destination terminal (MN2, H2; MN1, H1) via atleast one communication network (NW1; NW1, NW2), said at least onecommunication network comprising at least one mobility agent entity(HA1, HA2, AR1, AR2, ERn, ERm)) for each of said terminals, the methodcomprising the steps of: establishing a route (1, 2, 3, 4; 4, 5, 6, 7)from the source (MN1, H1; Ex, ENx) via at least one first mobility agent(AR1; ERn) associated to said source, at least two consecutivelyarranged second mobility agents (HA2, AR2; HA1, AR1) associated to saiddestination, to said destination (MN2, H2; MN1, H1), deciding that saidroute is to be optimized, and upon said decision, rerouting said routefrom one of said at least one first mobility agents (AR1; ERn) directlyto one of the at least two consecutively arranged second mobility agents(AR2; AR1) such that at least one intermediate mobility agent (HA2; HA1)in said route is bypassed in the resulting rerouted route.
 2. A methodaccording to claim 1, wherein said decision is taken at one of said atleast two second mobility agents (HA2, HA1) associated to saiddestination.
 3. A method according to claim 1, wherein said decision isbased on an indication by the source or destination to optimize theroute or to request for a specific quality of service for which routeoptimization is beneficial.
 4. A method according to claim 1, whereinsaid decision is based on a service type of the traffic between thesource and the destination.
 5. A method according to claim 4, whereinsaid decision to optimize the route is taken in case the service typeindicates a service imposing delay requirements.
 6. A method accordingto claim 4, wherein said service type indicates real-time traffic.
 7. Amethod according to claim 1, wherein said decision is based on anestimated benefit from route optimization between said source and saidterminal, and in case said estimated benefit exceeds a predeterminedthreshold value, it is decided to reroute said route.
 8. A methodaccording to claim 1, wherein said rerouting comprises the steps ofinforming one of said at least one first mobility agents of a currentcare_of_address of the destination.
 9. A method according to claim 8,wherein said informing comprises the steps of sending a message from oneof said consecutively arranged second mobility agents to one of saidfirst mobility agents including the current care_of_address of thedestination.
 10. A method according to claim 3, wherein said indicationtriggering the deciding for route optimization is included in a resourcereservation signaling.
 11. A routing system for routing data packetsfrom a source terminal (MN1, H1; Enx, Ex) to a destination terminal(MN2, H2; MN1, H1) via at least one communication network (NW1; NW1,NW2), said at least one communication network comprising at least onemobility agent entity (HA1, HA2, AR1, AR2, ERn, ERm)) for each of saidterminals, the system comprising: route establishment means adapted forestablishing a route (1, 2, 3, 4; 4, 5, 6, 7) from the source (MN1, H1;Ex, ENx) via at least one first mobility agent (AR1; ERn) associated tosaid source, at least two consecutively arranged second mobility agents(HA2, AR2; HA1, AR1) associated to said destination, to said destination(MN2, H2; MN1, H1), decision means adapted for deciding that said routeis to be optimized, and, rerouting means, adapted to perform in responseto said decision a rerouting of said route from one of said at least onefirst mobility agents (AR1; ERn) directly to one of the at least twoconsecutively arranged second mobility agents (AR2; AR1) such that atleast one intermediate mobility agent (HA2; HA1) in said route isbypassed in the resulting rerouted route.
 12. A system according toclaim 11, wherein said decision means is located at one of said at leasttwo second mobility agents (HA2, HA1) associated to said destination.13. A system according to claim 11, wherein said decision is based on anindication by the source or destination to optimize the route or torequest for a specific quality of service for which route optimizationis beneficial.
 14. A system according to claim 11, wherein said decisionis based on a service type of the traffic between the source and thedestination.
 15. A system according to claim 14, wherein said decisionto optimize the route is taken in case the service type indicates aservice imposing delay requirements.
 16. A system according to claim 14,wherein said service type indicates real-time traffic.
 17. A systemaccording to claim 11, wherein said decision is based on an estimatedbenefit from route optimization between said source and said terminal,and in case said estimated benefit exceeds a predetermined thresholdvalue, it is decided to reroute said route.
 18. A system according toclaim 11, wherein said rerouting means comprises informing means adaptedfor informing one of said at least one first mobility agents of acurrent care_of_address of the destination.
 19. A system according toclaim 18, wherein said informing means comprises sending means adaptedto send a message from one of said consecutively arranged secondmobility agents to one of said first mobility agents including thecurrent care_of_address of the destination.
 20. A system according toclaim 13, wherein said indication triggering the decision means fordeciding for route optimization is included in a resource reservationsignaling.